Flow retarders for fire tubes of boilers



Jan. 31, 1967 1.. R. LUCHFORD E TAL 3,301,276

FLOW RETARDERS FOR FIRE TUBES OF BOILERS Filed Sept. l4, 1964 3 Sheets-Sheet 1 2 N l FIG! 7 4 ek as ax 3. 1.. M

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1967 L. R. LUCHFORD ETAL 3,301,276

FLOW RETARDERS FOR FIRE TUBES OF BOILERS Filed Sept. 14, 1954 3 Sheets-Sheet 3 FIGJO INVENTORQ QWQ eus. a

United States Patent G 3,301,276 FLOW RETARDERS FOR FIRE TUBES F BQILERS Laurence Richard Luchford and Thomas Arthur Babbage, East Molesey, England, assignors to Trianco Limited, East Molesey, England Filed Sept. 14,- 1964, Ser. No. 396,015 Claims priority, application Great Britain, Sept. 18, 1963, 36,7 53/ 63 2 Claims. (Cl. 138-38) This invention relates to flow retarders for insertion in the fire tubes of boilers in order to retard flow of combustion gases therethrough and to secure effective contact of the gases with the walls of the tubes.

From one aspect, the invention provides a retarder comprising a tapering metal body having a plurality of longitudinally extending fins, the outer edges of which are parallel to the axis of the body, these fins serving to locate the retarder centrally in a fire tube of a boiler so that a number of passages of cross section gradually decreasing in area from bottom to top of the retarder are defined between the retarder and the fire tube.

From another aspect, a retarder in accordance with the invention for use in fire tubes of rectilineal sect-ion comprises a tapering metal body of corresponding cross-section, closed at the bottom and increasing in area from the bottom to the top, and provided with a plurality of longitudinally extending fins at the corners of the rectilineal section, the outer edges of these fins being parallel to the axis of the retarder and being adapted to engage the tube section to locate the retarder in the tube so that a plurality of tapering passages is defined between the sides of the retarder and the sides of the tube.

From yet another aspect, the invention provides a method of fabricating a retarder which comprises bending the opposite sides of a rectangular metal plate upwardly about two lines converging towards one another for a length extending at least partially from the top to the bottom edges of the plate and equally inclined to the length of the plate, and assembling a plurality of such plates with the bend lines of adjacent plates in contact so as to form a close polygonal figure.

This method produces a retarder which is of increasing polygonal section from bottom to top and which has a plurality of extending flanges with outer edges parallel to the longitudinal axis of the retarder. When such a retarder is inserted in a fire tube of section corresponding to that defined "by these outer edges, these edges locate the retarder and tapering passages are defined between the retarder and the tube.

The edges of the plates may be bent up at right angles and the plates welded along the bend lines. In this case, the flanges contact the sides of the tubes and tapering passages are formed at the corners as well as at the sides of the tube. In another form the edges of the plates are bent up at such an angle that the flanges of adjacent plates contact one another and can be welded together. In this case the flanges engage in the corners of the po lygonal section of the tube in which they are inserted. In the preferred form where the tube is of square section, the angle at which the flanges are bent up is 45.

The lower end of the retarder is closed preferably by a pyramidal bottom member. This can be an end cap of metal secured on the bottom of the retarder and such an end cap may be formed by pressing, welding a number of triangular pieces together or in any other convenient manner, or by forming a maltese cross of metal and bending up the arms of this cross so that the edges of adjacent arms are in contact.

Alternatively, the pyramidal end closure of the retarder may be formed by providing each plate with a triangular 3,301,276 Patented Jan. 31, 1967 portion extending from the bottom of the plate and bending these triangular portions inwardly so that their edges contact one another.

The bottom of the retarder may be closed by a plug of fire brick or other refractory material which may have a pyramidal or domed exterior.

The top end of the retarder may be closed by a cap which may conveniently consist of a metal plate located within the retarder on dimples or ridges in the side walls of the retarder and secured by welding. This retains the shape of the retarder internally and also prevents heat from within the retarder being lost freely into the flue. The retarder may be filled with suitable expanded insulating material such as slag wool.

The retarder may be fitted with a loop to enable it to be lifted freely. This loop may be formed by a metal strip extending across the top of the retarder and bent centrally to form a lifting eye. The protruding ends serve to locate the retarder in position. The metal strip is arranged so that its narrow edge is presented to the gas flow and so offers little or no resistance thereto.

The retarders may be'of tapering circular section to.

FIG. 1 is a plan view of a plate, four of which are bent and assembled to form the core of a generally squaresectioned retarder.

FIG. 2 is a central section of a completed retarder employing the plates of FIG. 1.

FIG. 3 is a central section of an alternative form of retarder.

FIG. 4 is an end view in the direction of arrow IV on FIG. 3.

FIG. 5 is a plan view of one of a pair of plates used in the construction of another alternative form of retarder.

FIG. 6 is an end view of the plate of FIG. 5 after bending.

FIG. 7 is a plan view of one of another pair of plates used in the construction.

FIG.- 8 is an end view of the plate of FIG. 7 after bending.

FIG. 9 is a central section of a completed basic core employ-ing plates shown in FIGS. 5 to 8.

FIG. 10 is a side view of a complete retarder taken at right angles to FIG. 9.

, FIG. 11 is an end view in the direction of the arrow XI on FIG. 10.

The form of retarder shown in FIG. 2 is for use in fire tubes of square section. It is formed from four simialr steel plates A, each rectangular in shape with a triangular portion B extending centrally from the bottom end, the base 3 of this triangle being less than the width of the plate. From the intersection of the inclined sides of the triangle with the bottom of the rectangle, bend lines 1 and 2 are drawn to the top end of the rectangle. These lines are oppositely inclined at the same angle to the centre line of the plate and diverge from one another from the bottom to the top of the rectangle.

The sides of the rectangle are bent upwardly at along these bend lines 1 and 2 and the triangular portion is bent downwardly about its base. The four plates are then assembled to form a square with the bend lines 1 and 2 of adjacent plates in contact with one another and the plates are welded together along the bend lines. This forms a frusto-pyramidal body of square section with flanges 4 and 5 extending from the sides, the outer edges of these flanges being parallel to one another and to the axis of the retarder.

v The sloping sides of the triangles also contact one another and are welded together to forma pyramidal closure 6 to the bottom of the retarder.

The top of the retarder is closed by an inserted metal plate 7 located by dimples 8 projecting inwardly from the walls of the retarder and welded in position.

A metal rod 9 is bent into U shape at its centre with aligned limbs extending from the ends of the U. The handle thus formed is welded across the top of the retarder, the limbs protruding beyond the retarder.

The retarder is inserted in the tube (not shown) and is located lengthwise by the protruding limbs of the handle; the flanges 4 and 5 engage the sides of the tube locating the retarder against sideways movement. Tapering passages, gradually decreasing in cross section from bottom to top of the retarder are then formed between the sides of the retarder and the sides of the tube and also at each corner of the tube between the flanges on adjacent sides of the retarder. The passage for the combustion gas is thus reduced towards the top and a relatively constant rate of gas flow is maintained as the gases contract upon cooling.

Referring now to FIGS. 3 and 4 it will be seen that tapered flanges 14 and 15 are formed at the corners of the retarder by bending the edges of plates A from which it is constructed to subtend angles of 135.

The bent edges are spot welded together as indicated to form a tapered core and triangular portions B are welded at their edges to form a pyramidal end cap.

An alternative constructional form of retarder is shown in FIGS. 5 to 11.

A plate C shown in FIG. 5 is notched centrally in both edges and :bend lines 11 and 12 are drawn from the apex of each notch at small divergent angle to the top edge of the plate.

The metal outside the bend lines is then bent through 90 to form flanges 24 and 25 and extended flats 26 and 27 as shown in FIG. 6. A pair of such plates is used in conjunction with a complementary pair of plates to form the basic core of the retarder, such aplate being shown in FIGS. 7 and 8. a

The complementary plate D is notched similarly to the plate C and has bend lines 11a and 12a which converge at a small angle towards the bottom edge of the plate. The metal outside the bend lines is bent through 90 to form convergent flanges 24a and 25a and extended fiats 264 and 2711 as shown in FIG. 8,

The two pairs of plates C and D are assembled with end plates E and F to form a generally square-sectioned core.

As can be appreciated from FIG. 9, the tapered flanges 24a, 25a of the plates D are spot Welded to the flats 25 and 27 of the plates C; similarly the flat 26a and 27a of the plate D are spot welded to the tapered flanges 24 and 25 of the plate C.

The end plate E is fitted with an extended bent rod han die 19, and the plate F is centrally apertured for the reception of a stainless steel bolt 20 by which a pyramidal cast iron cap 21 is fixed to the retarder core.

As in the earlier examples the handle and flanges pro vide for lengthwise and sideways location of the retarder within a square-sectioned fire tube.

It will be understood that the invention is not restricted to the preferred forms described by way of example which may be modified without departure fiom the scope of the following claims.

We claim:

1. A retarder for fire tubes of rectilineal cross section comprising a hollow, tapering metal body of corresponding cross-section, closed at the bottom and increasing in area from the bottom to the top, a plurality of longitudinally extending tapering fins at the corners of the rectilineal section of the body, the outer edges of said fins being parallel to the axis of the body and being adapted to engage the corners of a fire tube to locate the retarder in the tube so that a plurality of tapering passages is defined between the sides of the retarder and the sides of the tube, said fins each being comprised partially by extending flats of four plates constituting the tapering body and partly by tapering flanges bent up from such plates.

2. A retarder according to claim 1, wherein a pair of said four plates forming the body are each formed by tapered flanges bent at substantially from the lower portion of a flat plate about slightly converging bend lines, the other pair of said four plates being similarly provided with 90 flanges bent about converging bend lines in their upper portions, said fins then being formed, upon assembly of one plate from one pair and a complementary plate from the other pair, of the flat edge of said one plate and the 90 flange of said complementary plate.

References Cited by the Examiner UNITED STATES PATENTS 154,203 8/ 1874- Wilkinson 13838 1,557,249 10/ 1925 Gooseide 13840 2,291,985 8/1942 Powers 179 FOREIGN PATENTS 669,091 8/ 1963 Canada. 1,102,111 5/1955 France.

FREDERICK KETTERER, Primary Examiner,- 

1. A RETARDER FOR FIRE TUBES OF RECTILINEAL CROSS SECTION COMPRISING A HOLLOW, TAPERING METAL BODY OF CORRESPONDING CROSS-SECTION, CLOSED AT THE BOTTOM AND INCREASING IN AREA FROM THE BOTTOM TO THE TOP, A PLURALITY OF LONGITUDINALLY EXTENDING TAPERING FINS AT THE CORNERS OF THE RECTILINEAL SECTION OF THE BODY, THE OUTER EDGES OF SAID FINS BEING PARALLEL TO THE AXIS OF THE BODY AND BEING ADAPTED TO ENGAGE THE CORNERS OF A FIRE TUBE TO LOCATE THE RETARDER IN THE TUBE SO THAT A PLURALITY OF TAPERING PASSAGES IS DEFINED BETWEEN THE SIDES OF THE RETARDER AND THE SIDES OF THE TUBE, SAID FINS EACH BEING COMPRISED PARTIALLY BY EXTENDING FLATS OF FOUR PLATES CONSTITUTING THE TAPERING BODY AND PARTLY BY TAPERING FLANGES BENT UP FROM SUCH PLATES. 